Non-shingling forms feed tractor

ABSTRACT

This is an improved sprocket pin type forms feeding device used in the feeding of continuous, series connected, marginally perforated, multi-layered record forms. The sprocket pin type forms feeding device for multi-layered paper strips comprises a pair of sprocket wheels mounted on a rotatably driven shaft, with the sprocket wheels including a tractor drum portion having a base diameter and a tractor tire element securely attached to the tractor drum for increasing the base diameter so as to functionally overdrive the last or bottom-most copy of the multilayered forms at the same rate of speed as the first copy and to thereby prevent shingling of the paper layers of the multilayered forms.

United States Patent [191 Bonafino [111 3,838,804 [451 Oct. 1, 1974 [75] Inventor:

[ NON-SHINGLING FORMS FEED TRACTOR Edward J. Bonafino, Endwell, NY.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

Primary Examiner-Richard A. Schacher Attorney, Agent, or Firm--Charles S Neave ABSTRACT This is an improved sprocket pin type forms feeding device used in the feeding of continuous, series connected, marginally perforated, multi-layered record forms. The sprocket pin type forms feeding device for multi-layered paper strips comprises a pair of sprocket wheels mounted on a rotatably driven shaft, with the sprocket wheels including a tractor drum portion having a base diameter and a tractor tire element securely attached to the tractor drum for increasing the base diameter so as to functionally overdrive the last or bottom-most copy of the multi-layered forms at the same rate of speed as the first copy and to thereby prevent shingling of the paper layers of the multilayered forms.

4 Claims, 3 Drawing Figures NON-SHINGLING FORMS FEED TRACTOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the improvements in sprocket pin strip forms feeding devices, and particularly, to the feeding of forms having multi-layered copies wherein the driving tractor drum includes means for driving the last copy of the multi-layered form at the same rate of speed as the first copy to prevent shingling of the forms. With more particularity, the invention relates to improvements in forms feeding device for printers of the type disclosed in the U.S. Pat. No. 3,747,820 issued to .l. E. Hawxhurst and assigned to the assignee of the present invention.

2. Description of the Prior Art Forms feeding carriages are known in which tractors having endless belts with pins are used to feed continuous forms such as shown in U.S. Pat. No. 2,302,704, which issued Nov. 24, 1942, to C. R. Mabon. Another sprocket-type paper strip advancing mechanism is disclosed in the U.S. Pat. No. 3,028,063, which issued Apr. 3, 1962 to R. E. Busch et al. In the latter mentioned patent, there is disclosed structure whereby the paper is drawn through the machine by a friction roller and a sprocket roller spaced apart and operating in unison. The sprocket is carried by a shaft. The roller and sprocket have reduced diameter sprocket sections over which is fitted an endless cog belt which forms the driving means for driving the roller at the same angular speed as the sprocket is driven. The roller has two relatively soft sleeves of rubber to frictionally drive the paper strip. The outer diameters of the roller sleeves are slightly larger than the diameters of the sprocket section about which the paper strip is wrapped. Since the roller is intermediate of the drive sprocket and the source of frictional drag, the roller will tend to frictionally drive the paper ahead of the sprocket. Therefore, no load will be applied to the sprocket pins at this time.

Such a paper drive mechanism is satisfactory in certain paper feeding applications, but involves excessive equipment including the intermediate roller apparatus which utilizes more space and increases the cost of the mechanism. Further, experimentation with such an apparatus has caused a cyclical bunching of the forms in the printing area.

SUMMARY OF THE INVENTION The present invention is based on applicants discovcry that by utilizing a tractor roller having an increased radius in frictional engagement with the paper being driven by .the feed sprocket that this arrangement can functionally operate to overcome the undesired shingling characteristics generally present when feeding multi-layered paper forms.

Briefly, the forms feeding apparatus particularly adapted for feeding multi-layered paper strips comprises a pair of sprocket wheels mounted on a rotatably driven shaft and wherein the sprocket wheels include a tractor drum portion having a base diameter. A tractor tire element or equivalent structure is securely attached or snapped onto the tractor drum for the purpose of increasing the diameter of the tractor drum.

The tractor drum structured in this manner frunctions to overdrive the last or bottom-most copy of the multilayered forms at the same rate of speed as the first copy. This action prevents the shingling of the intermediate and bottom-most paper layer of the paper forms being fed by the paper feeding apparatus.

It is a primary object of this invention to provide a simple and inexpensive improved fonns feeding apparatus for a printer device.

Another object of this invention is to provide a forms feeding apparatus which can accommodate a wide range of multi-layered paper forms.

It is also an object of this invention to provide a forms feeding apparatus having a pair of separate sprocket wheels including a frictional paper drive drum to drive the last or bottom-most copies of a multi-layered paper strip in a manner to eliminate shingling of the various layers.

The foregoing and other objects, features and advantages of the invention will be apparent from the following, more particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF PREFERRED EMBODIMENT Referring particularly to FIG. 1 of the drawings, the reference numeral 10 denotes generally one of two forms feeding devices used for feeding continuous forms or document 12 past a print line defined by a type character 14 representing a chain or train of characters, which move along a print line perpendicular to the surface of the drawing past a plurality of print hammers represented by the hammer 116 comprising an armature pivotally supported at 18 to be actuated by means of a solenoid 20 for impacting the document 12 against the type characters 14 for printing on the document.

The forms feeding device 10 may comprise a pair of sprocket wheels 22 (FIG. 3) positioned in spaced apart relation for feeding the continuous forms 12. The sprocket wheel 22 is mounted on a support shaft 24, which spans between two end plates (not shown). The sprocket wheel 22 is provided with a plurality of sprocket pins 28 about its periphery for engaging holes 13 in the continuous forms 12.

Referring to FIGS. 1, 2 and 3, the sprocket wheel 22 i has a tractor drum surface 30 adjacent the sprocket wheel 22. The sprocket wheel 22 is mounted on a shaft 24 by being secured to a relatively flat carrier plate 34 t When multi-layered forms are being fed or advanced by a round tractor, the different layers of the forms tend to shingle. This is due to the fact that the paper is e where F 2 l i is the force differential about the tractor; e equals 2.718 The base of Napierian or hyperbolic logarithms, y. equals the coefficient of friction between the tractor and the paper; and (1 equals the included angle in radians by which the paper wraps around the drum.

According to the invention, the increasing of the radius R at a point on the tractor drum 30 such that the frictional drive force derived from the drums 30 to the last copy of the multi-layer form compensates for the drag in the paper feed path on the last copy and drives the last copy at least the same distance as the copies being driven only by the sprocket pins 28 of the tractor drum assembly. The base diameter herein referred to is the diameter of the sprocket wheel 22. Generally, in forms feeding apparatus the tractor drum has the same base diameter as the sprocket wheel 22. To achieve the intended result, the base diameter of the tractor drum 30 is-increased in the order of from 0.015 to 0.070 inch by the addition of a tractor tire element 40 securely attached to or snapped on the tractor drum 30. The tractor tire element 40 is fabricated of a material having a high coefficient of friction characteristic. In a preferred embodiment of the apparatus the tractor tire element 40 was fabricated of urethane material. The tractor tire element 40 can be added to the tractor drum 30 by coating the drum in that area or by snapping a tire of the appropriate material onto the drum or securing it thereto.

The utilization of a pair of sprocket pin type forms feeding devices fabricated in the above explained manner functions to feed multi-layered paper forms so as to eliminate the shingling characteristics which are usually attendant when feeding paper forms over and around tractor devices.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is: t

1. A sprocket pin type forms feeding device for continuously advancing multi-layered paper strips comprising:

a. a continuously and rotatably driven shaft;

b. a pair of axially spaced sprocket wheels each having sprocket pins engageable in perforations along the edges of the multi-layered paper strips for advancing same and concentrically mounted and secured on said continuously and rotatably driven shaft, said sprocket wheels including a tractor drum portion having a base diameter; and a tractor tire element securely attached to the tractor drum portion immediately adjacent to each of said sprocket wheels for increasing the diameter of the tractor drum portion and functioning to frictionally engage and overdrive the last copy of the multi-layered forms at the same rate of speed as the first copy and thereby prevent shingling of the paper layers of the forms.

2. A sprocket pin type forms feeding device as defined in claim 1 wherein the tractor tire element is fabricated of a material having a high coefficient of friction characteristic.

3. A sprocket pin type forms feeding device as defined in claim 1 wherein the tractor tire element is fabricated of urethane material.

4. A sprocket pin type forms feeding device as defined in claim 2 wherein the tractor tire element increases the base diameter of the tractor portion in the range of 0.015 inches to 0.070 inches. 

1. A sprocket pin type forms feeding device for continuously advancing multi-layered paper strips comprising: a. a continuously and rotatably driven shaft; b. a pair of axially spaced sprocket wheels each having sprocket pins engageable in perforations along the edges of the multilayered paper strips for advancing same and concentrically mounted and secured on said continuously and rotatably driven shaft, said sprocket wheels including a tractor drum portion having a base diameter; and c. a tractor tire element securely attached to the tractor drum portion immediately adjacent to each of said sprocket wheels for increasing the diameter of the tractor drum portion and functioning to frictionally engage and overdrive the last copy of the multi-layered forms at the same rate of speed as the first copy and thereby prevent shingling of the paper layers of the forms.
 2. A sprocket pin type forms feeding device as defined in claim 1 wherein the tractor tire element is fabricated of a material having a high coefficient of friction characteristic.
 3. A sprocket pin type forms feeding device as defined in claim 1 wherein the tractor tire element is fabricated of urethane material.
 4. A sprocket pin type forms feeding device as defined in claim 2 wherein the tractor tire element increases the base diameter of the tractor portion in the range of 0.015 inches to 0.070 inches. 